| Negative thermal materials has been a research hotspot from recently, due to Controllable coefficient of thermal materials can be prepared by means of composite with ZrW2O8,so its application is very extensive. In ceramic materials, ceramics with near-zero thermal expansion has significant advantage in thermal shock resistance, can prolong the service life of ceramic.Cubic ZrWiO8 exhibits large isotropic negative thermal expansion over its entire stability range from 0.3K to1050K.thus becomes the research focus in negative expansion material. The study of Preparation and application are very extensive In the domestic and overseas, but up to now,there is no comprehensive reach.In this study,we have a choice of the raw materials that frequent used when prepare ZrW2O8,and we prepared ZrW2O8 materials by using the hydrothermal method, coprecipitation method and solid phase method three kinds of methods. The influence factors of each kind of methods are study comparatively. And the best conditions was given.In addition to that we use saline direct sintering obtained the good effect.The results analyzed by means of XRD and SEM were showed that the best preparation conditions using hydrothermal method was that:Usingcoprecipitation preparation best preparation conditions of pH= 4,0.5 h under 1180℃ heat treatment, powder crystallinity and morphology arebetter; Hydrothermal temperature 200℃, hydrothermal time 18 h, pH= 4, heat treatment is carried out under the 650 ℃by this good crystallinity, relatively regular shape and particles are fine powder was prepared; Using solid phase method, due to the sintering time is too long use the traditional solid phase method, Solid phase method step by step was too trouble, in this study,we directly use salt as raw materials mixed grinding sintered,1.5 h under 1180℃heat treatment,we gea-ZrW2O8 powder and the coefficient of thermal exoansion is-6.O×10-6/K, this method less time consuming,and the operation is simple. |
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